Patent GB-531216-A (GB)
Title: Improvements relating to electric signalling systems
IPC: H04Q3/00
Filed: 1939-07-14
Abstract: 531,216. Electric signalling systems. SIEMENS BROS. & CO., Ltd., CHRISTIAN, D. A., and DURKIN, E. W. July 14, 1939, No. 20535. [Class 40 (i)] [Also in Group XXXIX] Different signals are transmitted as pulses of different durations which are timed by a cyclically operating device performing one or more cycles, and in a two-way signalling system the device is also used to determine the durations of received impulses. The signals may be of direct current or of high or low frequency alternating current. The invention is described for D.C. signalling arrangements between the terminals of a two-way carrier channel and associated exchanges. In the arrangements shown, Fig. 1 comprises exchange equipment in which outgoing calls are set up over jack OGJ and incoming calls are routed to terminals ia ... id and thence over a repeater Fig. 2, to an incoming selector. Signalling between the exchange equipment and the junction terminal is effected over wires c, d, the arrangements at one end of the junction comprising a dry loop A, Fig. 1, at the exchange and a wet loop (battery feed) A, Fig. 3 at the junction terminal, and converse arrangements B, Figs. 1 and 3, at the other end of the junction. Release signals are longer than calling and answering signals, the timing of outgoing and incoming signals being effected by a slow self-interrupting relay IR, Fig. 1, of the kind described in Specification 462,773, [Group XXXIX], in conjunction with counting relays CA, CB, the short signals being timed by one cycle of IR and the release signal by two. Outgoing call. Relay PC is normally held operated over its R.H. winding. On jack OGJ being plugged, sleeve relay S pulls up followed by SS whereupon flicker pulse equipment is started and flicker wire FE connected to the sleeve. Impulse repeating relay EA operates a start relay BO and relay ET operates the busy lamp relay ELR. Relay BO releases PC by making a differential circuit over its L.H. winding whereupon P pulls up, starts the selfinterrupting relay IR and completes the signal circuit at equipment A or B. High speed relay X is also operated by P. When IR is operated, CA follows, and at its early armature ca1 shunts down X before CA fully operates and thereby prevents the operation of CB at this time. CA also re-operates PC over its L.H. winding leaving P dependent on IR the relapse of which terminates the pulse, CA relapsing but BO remaining held. This signal conditions the distant terminal to receive impulses. The dialling key operates RR to connect impulse relay EA to the ring conductor, DT being also operated to shunt the repeating coils, 'and LR being connected in the sleeve circuit to remove the flicker. Impulses are repeated by EA to the junction terminal. When the called party replies a short backward pulse operates JA, JB, relay IR is started and B1 pulls up, P being prevented from operating and PC from changing its condition. Relays X, IR, CA function as before and when JA, JB fall back on termination of the pulse, OS pulls up locks and throws both windings of S into the sleeve circuit to dim the lamp. B1 also restores so that P and PC may function on the forward release signal. When the called party hangs up, a double length pulse operates JA, JB for two cycles of IR so that both CA, CB pull up and an opposing upper winding of OS causes this relay to release and light the supervisory lamp. On withdrawal by the operator, S, SS, EA, ET, BO release so that PC which has been holding over its L.H. winding falls back by operation of the R.H. winding, P pulls up, starts IR and sends out a pulse. After the first cycle of IR, P remains held since PC is not re-operated (BO back), so that IR operates on the second cycle, both CA and CB are energized and PC is re-operated to make P dependent on IR, the relapse of which on the second cycle releases P followed by CA, CB. Incoming call. The short incoming pulse operates JA, JB and BI, with results as previously described except that since BO is not operated, IS pulls up instead of OS, and completes a connection over wire ic to operate relay A at the repeater, Fig. 2. Relays ET, ELR operate to light the busy lamps and the shunt on the L.H. winding of CA is removed. The dialled impulses are repeated by JA to A and as JB also operates, relay IR will be started. In order to make this relay ineffective as regards CA, CB, a left hand opposing winding of CA is energized on the relapse of JB to release it before IR can re-operate on the second cycle. On reply of the called party, ground on wire id operates DA which releases PC by differential action so that P pulls up, starts IR and sends back a pulse, DA being held for its duration. IR, X, CA operate as before and PC pulls up to make P dependent on IR which terminates the pulse. When the called party hangs up, DA relapses followed by PC and P pulls up to send out a long pulse since it is not released by the first relapse of IR. CB pulls up on the second cycle and operates PC over its R.H. winding so that P falls back on the second relapse of IR. The effect of the incoming long release signal will be understood from previous description, the operation of CB on the second cycle and the relapse of JB on termination of the pulse releasing IS by means of its upper opposing winding so that the circuit restores to normal. The relapse of IS also releases the repeater. Guard against false signals ; testing speed of IR. The period of operation of IR guards against signals which are too short. If it is desired to guard against signals of excessive length, each signal on receipt may cause transmission of a reverted signal which is followed by a confirmatory signal in the case of a proper pulse signal and a cancelling signal in the case of a false one. The speed of operation of IR is tested by plugging jack TJ so that PR is impulsed and transmits to a counting device such as that described in Specification 471,987 which gives an indication every 10th impulse. Junction terminals, Fig. 3. These terminals operate in conjunction with carrier equipment in an obvious manner, the pulses in the two directions being repeated by AA and DD. If the P relays at the exchanges at both ends of the junction are simultaneously operated, the operation of DD at B at one terminal will be without effect on relays JA, JB on equipment B at the corresponding exchange, whereas the operation of DD at the terminal A will control JA, JB at equipment A at the other exchange. Incoming repeater, Fig. 2 ; busy flash. Relay A responds to the calling impulse followed by B and I. When the impulse trains come in C, BB and MD pull up, but C falls back at the end of each train. When the called party replies, D releases MD which operates DD to ground the signalling wire id whereby a short backward signal is transmitted as previously described. When the called party hangs up, D and DD relapse to bring about the long back release signal. The long clearing signal from the distant end releases A and other operated relays. If the wanted line is busy intermittent battery is applied to both wires, I and BB being released on the first application but on the reoperation of I, BR is operated and holds MD to shunt the impulse repeating contact in the loop. On the following relapses of I, DD is operated to cause the backward transmission of pulses by grounding wire id.